hy/core/macros.hy: Add defn-alias / defun-alias

In the same vein as defmacro-alias, this implements defn-alias /
defun-alias, which does essentially the same thing as defmacro-alias,
but for functions.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
hy/core/macros.hy: Add an (if-not) macro

Sometimes it is better to start with the false condition, sometimes that
makes the code clearer. For that, the (if-not) macro, which simply
reverses the order of the condition blocks, can be of great use.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
hy/core/macros.hy: Reimplement (unless) in terms of (if-not)

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Adding a simple `identity' function

* hy/core/language.hy: Adding a simple `identity` function that returns
  the argument supplied to it

* docs/language/core.rst: Updated docs with identity function
Merge branch 'master' into pr/456
Merge branch 'master' into pr/461

Conflicts:
	tests/native_tests/native_macros.hy
Merge branch 'master' into pr/468
Reorganize documentation.
Document hyc command line options.
Merge pull request #474 from berkerpeksag/hyc-doc

Document hyc command line options.
Add `items`, `values` and `keys` methods to HyDict

Useful for macros, for example:

    (defmacro defn-checked [n x b]
      `(defn ~n [(unquote-splice (.keys x))]
        (print "Expecting:" (unquote-splice (.values x))) ~b))

    (defn-checked hello {name str age int}
      (print "Hello" name "you are" age))

    (hello "Godzilla" 60)

    ;; Expecting: <type 'str'> <type 'int'>
    ;; Hello Godzilla you are 60
Add tests for HyDict methods
Add Brian McKenna to AUTHORS
Fix single spaces between methods in test_dict.py
Attempt to fix HyDict#items for Python 3

Looks like Python 3 changed `zip` to returning an iterable and not a
list. We should be good to just wrap the call in `list`.
Add integer-char? to core
Merge pull request #480 from agentultra/digit-char

Add integer-char? to core
README.md: Add Adderall to Hylarious Hacks

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
Merge master onto pr/473
Merge master onto pr/482